Breast tissue contains several types of collagen including type I and type III collagen in the stromal compartment and type IV collagen in basement membranes. Little is known about the regulation of collagen metabolism in normal and neoplastic breast tissue. It has been suggested that altered collagen metabolism is involved in the pathological growth and spread of metastases which are characteristic of malignancy. It has also been shown that the inhibition of type IV collagen synthesis blocked the growth of normal mammary gland and certain mammary tumors in rats. The objective of this proposal is to understand the regulation of collagen metabolism in normal and neoplastic rat and human breast tissues, particularly with respect to hormonal influences. I would also like to investigate the effects of cis-hydroxyproline and collagen metabolism in the growth of cultured human breast tumor explants. Collagen synthesis will be measured in tissue minces and in cultured cells by the incorporation of tracer amino acids into collagenase sensitive, antibody-precipitable procollagen. Collagenase will be assayed in the medium of cultured explants and cells following activation by trypsin or chaotropic agents. Radiolabeled type I and type IV collagens will be used to measure the collagenases specific for each substrate. Plasminogen activator, which is believed to be involved in collagenase activation, will be assayed by the plasminogen-dependent degradation of fibrin. Cell proliferation and carcinogenesis will be investigated by analyzing collagen synthesis and degradation in normal virgin, perphenazine-stimulated, and N-nitrosomethylurea (NMU)-treated rat mammary gland and in NMU-induced rat mammary tumors. Ovarian-dependent and ovarian-independent mammary tumors, cultured tumor explants, estrogen-responsive and estrogen-unresponsive mammary epithelium and fibroblasts will be analyzed for the effects of hormones and factors which affect growth. The mechanism of collagenase regulation will be studied to determine the level at which controls exist. Understanding the role of hormones in the normal and pathological interaction of cell types should prove collagen metabolism to be a worthwhile target for the therapeutic manipulation of malignant growth and metastasis.